Prevent the SEO score filter from displaying on a post type overview page if the metabox has been hidden for the post type as suggested by [coreyworrell](https://github.com/coreyworrell) in issue [#601](https://github.com/Yoast/wordpress-seo/issues/601).
Two typos as reported in #605
Removed the `pt_is_public()` method in favour of `is_metabox_hidden()` method -> better solution for issue [#601](https://github.com/Yoast/wordpress-seo/issues/601).
Merge remote-tracking branch 'jdevalk/release/1.5' into Fix-settings-issues